In a communications system that includes a macro base station (Macro BS), a small cell (Micro Base Station (Micro BS))/Pico Base Station (Pico BS), and user equipment (UE), the small cell is a base station accessed by UE, and directly serves UE such as a mobile phone, and the Macro BS may connect to a core network using a wired or microwave communication link or the like. A problem in the communications system is how to transmit service data of a terminal user to the Macro BS.
Currently, the foregoing problem is usually resolved using the following two solutions. One solution is to use a wired connection such as a cable or a fiber, but both wiring costs and manpower costs of this solution are extremely high. The other solution is to use a wireless backhaul technology. The wireless backhaul technology may be a microwave, or may be a low-carrier wireless technology based on WI-FI, the 802.16 protocol, or Long Term Evolution (LTE). In order to reduce power and network interference, the wireless backhaul technology generally uses a directional antenna.
The directional antenna is used in the wireless backhaul technology. Therefore, if a signal transmission direction is not aligned with a destination antenna, that is, a maximum gain point of a transmit antenna and a maximum gain point of a destination antenna are not aligned, signal quality is deteriorated, or power is wasted severely. Therefore, how to implement antenna alignment becomes an important problem that needs to be resolved in the wireless backhaul solution.
Compared with a high frequency signal, a low frequency signal has a lower data transmission rate, a wider field of view of a low frequency beam, a lower frequency, and lower power consumption of data transmission and exchange. Compared with a low frequency signal, a high frequency signal has a higher data transmission rate, a narrower field of view of a high frequency beam, a higher frequency, and higher power consumption of data transmission and exchange.
When a frequency of a radio frequency (RF) antenna is relatively low, a field of view of a low frequency antenna beam is relatively wide, and beam alignment does not need to be performed when a low frequency antenna is accessed. When the frequency of the RF antenna is relatively high, a field of view of a high frequency antenna beam is relatively narrow, and high frequency beam alignment of a high frequency antenna needs to be performed when a high frequency antenna is accessed. However, because a field of view of a high frequency beam is narrow, high frequency beam alignment is relatively difficult, and costs a relatively long time.